An active execution of the tilting movement, although necessary for younger children, was not sufficient
to enable successful mental transformations. Even with an active tilting movement, visual
information was crucial for a continuous mental transformation. Visual information about the glass
movement might provide a reference frame for the to-be imagined water inside the glass or might allow
smooth pursuit eye movements and, thereby, help to smoothly transform the mental representation
of the water. One might conclude that this visual information is actually the key to successful
imagery performance and that tilting the glasses facilitates performance only by providing visual
information about the tilting movement.